Terahertz (THz) technology is a newly emerging field that has numerous applications in the medical imaging, defense, security, communications, and manufacturing industries. THz radiation refers to electromagnetic waves propagating at frequencies in the terahertz range, and is sometimes referred to as sub-millimeter radiation, terahertz waves, terahertz light, T-rays, T-light, or T-lux. THz typically applies to electromagnetic radiation with frequencies between the high-frequency edge of the microwave band near 300 GHz and the long-wavelength edge of far-infrared light near 3000 GHz. Wavelengths in this spectrum range from about 100 μm (infrared) to 1.0 mm (microwave).
THz waves usually travel in line of sight, and are capable of penetrating a wide variety of non-conducting materials. For example, THz radiation can pass through clothing, paper, cardboard, wood, masonry, plastic and ceramics. It can also penetrate fog and clouds, but cannot penetrate metal or water.
Parametrically generated oscillations have been produced via parametric instability between two coupled oscillators, and has been theoretically studied and experimentally observed in opto-mechanical systems, with parametric coupling achieved through radiation pressure. In these studies, researchers were able to create sustained oscillations at radio frequencies in micro-mechanical resonators. Certain designs have produced continuous wave THz radiation by directing light from two lasers into a non-linear medium or photoconductive antenna. Despite the promising applications of this technology, the availability of compact, reliable sources of THz waves is still limited.